The present invention provides an improved system for controlling the location of sliding electrical contacts relative to a rotor.
A wide variety of different types of electrical machinery, such as DC motors, employ one or more rings of sliding electrical contacts or brushes in contact with a rotor. One such item, called a homopolar machine, has recently become the subject of intensive research as a storage device for energy. The homopolar machine includes a large fly wheel, and energy is stored as kinetic energy through rotation of the fly wheel. Energy is tapped from or delivered to the fly wheel as a pulsing electric current when one or more rings of sliding electrical contacts are placed in contact with a rotor which rotates with the fly wheel.
A problem with all electrical devices using sliding contacts with a rotor, and a special problem with homopolar devices as described above, is the heat loss and wear caused by friction between the sliding electrical contacts and the rotor. Since a homopolar machine is designed to be a mechanism for the storage of energy, excessive loss of energy through friction substantially defeats the purpose of the device. The contacts are usually constructed of liquid metal to reduce friction, but the friction still remaining seriously degrades the feasibility of homopolar machines.
In order for a homopolar machine to be feasible from an energy conservation standpoint, precise control of the pressure between the sliding electrical contacts and the rotor to achieve a good electrical connection without undue friction is required. Also, with such homopolar machines it is usually desirable to move the sliding electrical contacts into and out of contact with the rotor relatively frequently.
In the past, different types of systems have been the subject of experimentation for moving the sliding electrical contacts relative to the rotor in a homopolar machine and other such devices. Hydraulic, pneumatic and solenoid systems have been developed, but none of these systems has achieved the desired efficiency in precisely controlling the location of the electrical contacts relative to the rotor, and the rapid cycling of the contacts into and out of contact with the rotor. As a result, friction losses between the contacts and the rotor remain a serious impediment to the development of an efficient homopolar device.